Two men were transported to the hospital in critical condition after there was an explosion Monday afternoon while they were working on tanks at the wastewater treatment plant.

Joyce Williams, Huron Valley Ambulance spokeswoman, said at 4:20 p.m. Monday that one of the men died at the University of Michigan hospital from the injuries he suffered.

The Washtenaw County Sheriff's Office has identified this man as Michael Koch. Koch was a 48-year-old Brooklyn, Mich., resident and he worked for Platinum Pneumatical Mechanical. According to an email sent to the Dexter Leader, Koch was raised in Dexter and is a former graduate of Dexter High School.

The other man was brought to stable condition, Williams said. The sheriff's office has identified him as David McBride, a 23-year-old Howell resident who works for Regal Recycling.

Dexter Fire Chief Loren Yates said a call came in for the explosion at about 1:39 p.m. at Dexter Utilities Department, 8360 Huron St.

The men were doing some construction at the site and were disassembling a tank when the explosion occurred, he said. Somehow some methane gas ignited as they were cutting steel, he said.

Williams said the men were left two stories up and required rescue when the call came in. They were blown onto the roof of an adjacent building from the explosion, she said.

Dieter Heren, police services commander for the Washtenaw County Sheriff's Office, said the cylinder-shaped tank they were working on is several stories high and attached to the Dexter Utilities building on the west side of the site. He said investigators have determined one of the men was right by the tank when the explosion occurred, but they have not confirmed where the other was positioned.

Both a technical rescue team and Survival Flight were called to respond, Williams said, with a road cleared so Survival Flight could land.

However, firefighters and paramedics already at the scene were able to get the men down, she said. She said at that point it was faster to transport them by ambulance to the University of Michigan Health System, and the technical rescue team and Survival Flight were called off.

Williams said the men arrived at the hospital by 2:33 p.m.

Besides Dexter firefighters and Huron Valley Ambulance, she said Chelsea firefighters also responded to assist.

Yates described the explosion as a flare up. He said it didn't set fire to the building and firefighters were able to focus on rescuing the two men and helping to treat them.

The sheriff's office is conducting an investigation into what happened and investigators were still at the site as of about 5:30 p.m. Monday.

Heren said investigators have not found any signs of foul play.

In addition to the investigation by the sheriff's office, he said the Michigan Occupational Safety and Health Administration (MIOSHA) is conducting a separate investigation. MIOSHA does investigations when there is a death at a work place like in this situation, he said.

Each investigation has its own focus, Heren said. He said the sheriff's office is looking into whether there is any criminal action that caused the explosion and MIOSHA is looking more into factors like workplace safety issues. Since there doesn't seem to be any indication of criminal activity, he said he expects MIOSHA to take the lead position in the investigation.

According to a statement sent out Tuesday afternoon, the sheriff's office is not investigating this incident as criminal. The sheriff's office expects MIOSHA will continue to look into the circumstances leading up to the accident and MIOSHA could take action.

Dexter Assistant Village Manager Courtney Nicholls said the injured men are contractors, not village employees. A change order request was underway.